Transcranial Doppler detection of microembolic signals during pulmonary vein antrum isolation: implications for titration of radiofrequency energy.

BACKGROUND: Cerebrovascular events are an important complication during pulmonary vein antrum isolation (PVAI). Microembolic signals (MES) have been associated with stroke and neurological impairment. However, the incidence of MES during PVAI, and their relationship to microbubble formation and radiofrequency (RF) parameters are unknown. OBJECTIVES: We sought to assess the relationship between MES, microbubble detection, and neurological outcome and the impact of RF titration strategy on these parameters. METHODS: We studied 202 patients in two groups undergoing PVAI using an intracardiac echocardiography (ICE)-guided technique. MES were detected by transcranial Doppler (TCD) using insonation of the middle cerebral arteries. The number of microbubbles on ICE were qualitatively labeled as FEW, MODERATE, and SHOWER. In group I (n = 107), RF output was titrated to avoid microbubble formation and in group II (n = 95), standard power-limited RF output was used. RESULTS: TCD detected MES in all 202 patients during PVAI with an average of 1,793 +/- 547 per patient; 90% were detected during left atrial ablation. Over 85% of MES occurred after microbubbles. Group I patients had significantly lower numbers of MES (1,015 +/- 438 per patient) compared to group II patients (2,250 +/- 864 per patient) (P < 0.05). Group II also had a 3.1% incidence of acute neurological complications versus 0.9% in group I (P = 0.10). Patients with clinical events had significantly higher numbers of MES. There were no significant correlations between RF power, temperature, or impedence and MES number. CONCLUSIONS: MES directly correlate to the amount of microbubble formation on ICE, and may result in cerebroembolic complications. Titration of RF according to microbubble formation by ICE during PVAI may be important for minimizing the occurrence of MES and possibly acute neurological complications.

Leukocyte count predicts microembolic Doppler signals during carotid stenting: a link between inflammation and embolization.

BACKGROUND AND PURPOSE: Protected stenting has emerged as a safe and effective alternative to endarterectomy for the treatment of carotid stenosis in patients at high operative risk. Distal microembolization occurs invariably during carotid stenting. Little is known about the relationship between systemic inflammation and embolization during carotid stenting. METHODS: We examined 43 consecutive patients who underwent carotid stenting with simultaneous transcranial Doppler (TCD) monitoring of the ipsilateral middle cerebral artery. Embolization was quantified by measuring microembolic signals (MES) on TCD. Preprocedure leukocyte counts were related to MES. RESULTS: In unadjusted analyses, preprocedure leukocyte count was positively correlated with total procedural MES (r2= 0.16; P=0.008). After considering age, gender, comorbidities, concomitant medical therapies, and the use of emboli prevention devices, increasing leukocyte count (beta=35 for each 1000/microL increment; P=0.018) remained a significant and independent predictor of embolization (model-adjusted r2=0.365; P=0.0005). CONCLUSIONS: Increasing preprocedure leukocyte count independently predicted more frequent MES during carotid stenting. These data suggest that systemic inflammation may influence the degree of procedural embolization.